AIDEGen: Merge multiple dependencies-module.iml files into a single dependencies.iml.

Originally, in multiple project case, each module has a dependency iml
file with name as dependencies-[module name].iml. If there exists any
duplicated source folder paths within the content of those iml files,
and when the user want to save any change in IntelliJ project structure
dialog, it fails with following message:
... two modules in a project cannot share the same content root.
This CL will merge all dependencies-[module name].iml files into a
single dependencies.iml to fix the issue.

Bug: 134513192
Test: 1. m aidegen; aidegen-dev Settings DocumentsUI
      2. Go to the IntelliJ window, choose File -> Project Structure ->
         Select "Modules" in Project Settings -> Select "Settings"
	 module, click "+" to add an "Android".
      3. Click "Apply" and success without any error.

Change-Id: I39e825fe6095622cee7eae15ad8b0e976943f251
5 files changed